A hydrodesulfurization process for residual hydrocarbons and employing a catalyst composition promoted with titanium is described in U.S. Pat. No. 3,840,473. As described therein, titanium is added to a Group VI-B and Group VIII metals-containing catalyst composition and the prepared catalyst composition, in sulfided form, is employed in the hydrodesulfurization of residual-containing liquid hydrocarbons.
Conventional shutdown procedures for residual hydrocarbon hydrodesulfurization processes involve passing a high velocity hydrogen-containing gas over the fixed catalyst bed during the cooling step. Utilizing this shutdown procedure, it was observed that the catalyst suffered a loss of activity and stability at startup following the shutdown. To correct this deficiency, it was necessary to presulfide the catalyst in a manner similar to that employed when the catalyst was fresh. This method of operation is unsatisfactory, particularly in those instances when the hydrodesulfurization unit must be shutdown because of an emergency.